Deuterated Idebenone

ABSTRACT

The present invention in one embodiment provides a compound of Formula I:(I), or a pharmaceutically acceptable salt thereof, wherein the variables shown in Formula I are as defined in the specification.

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/670,716, filed on Jul. 12, 2012. The entire teachings of the aboveapplication is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Many current medicines suffer from poor absorption, distribution,metabolism and/or excretion (ADME) properties that prevent their wideruse or limit their use in certain indications. Poor ADME properties arealso a major reason for the failure of drug candidates in clinicaltrials. While formulation technologies and prodrug strategies can beemployed in some cases to improve certain ADME properties, theseapproaches often fail to address the underlying ADME problems that existfor many drugs and drug candidates. One such problem is rapid metabolismthat causes a number of drugs, which otherwise would be highly effectivein treating a disease, to be cleared too rapidly from the body. Apossible solution to rapid drug clearance is frequent or high dosing toattain a sufficiently high plasma level of drug. This, however,introduces a number of potential treatment problems such as poor patientcompliance with the dosing regimen, side effects that become more acutewith higher doses, and increased cost of treatment. A rapidlymetabolized drug may also expose patients to undesirable toxic orreactive metabolites.

Another ADME limitation that affects many medicines is the formation oftoxic or biologically reactive metabolites. As a result, some patientsreceiving the drug may experience toxicities, or the safe dosing of suchdrugs may be limited such that patients receive a suboptimal amount ofthe active agent. In certain cases, modifying dosing intervals orformulation approaches can help to reduce clinical adverse effects, butoften the formation of such undesirable metabolites is intrinsic to themetabolism of the compound.

In some select cases, a metabolic inhibitor will be co-administered witha drug that is cleared too rapidly. Such is the case with the proteaseinhibitor class of drugs that are used to treat HIV infection. The FDArecommends that these drugs be co-dosed with ritonavir, an inhibitor ofcytochrome P450 enzyme 3A4 (CYP3A4), the enzyme typically responsiblefor their metabolism (see Kempf, D. J. et al., Antimicrobial agents andchemotherapy, 1997, 41(3): 654-60). Ritonavir, however, causes adverseeffects and adds to the pill burden for HIV patients who must alreadytake a combination of different drugs. Similarly, the CYP2D6 inhibitorquinidine has been added to dextromethorphan for the purpose of reducingrapid CYP2D6 metabolism of dextromethorphan in a treatment ofpseudobulbar affect. Quinidine, however, has unwanted side effects thatgreatly limit its use in potential combination therapy (see Wang, L etal., Clinical Pharmacology and Therapeutics, 1994, 56(6 Pt 1): 659-67;and FDA label for quinidine at www.accessdata.fda.gov).

In general, combining drugs with cytochrome P450 inhibitors is not asatisfactory strategy for decreasing drug clearance. The inhibition of aCYP enzyme's activity can affect the metabolism and clearance of otherdrugs metabolized by that same enzyme. CYP inhibition can cause otherdrugs to accumulate in the body to toxic levels.

A potentially attractive strategy for improving a drug's metabolicproperties is deuterium modification. In this approach, one attempts toslow the CYP-mediated metabolism of a drug or to reduce the formation ofundesirable metabolites by replacing one or more hydrogen atoms withdeuterium atoms. Deuterium is a safe, stable, non-radioactive isotope ofhydrogen. Compared to hydrogen, deuterium forms stronger bonds withcarbon. In select cases, the increased bond strength imparted bydeuterium can positively impact the ADME properties of a drug, creatingthe potential for improved drug efficacy, safety, and/or tolerability.At the same time, because the size and shape of deuterium areessentially identical to those of hydrogen, replacement of hydrogen bydeuterium would not be expected to affect the biochemical potency andselectivity of the drug as compared to the original chemical entity thatcontains only hydrogen.

Over the past 35 years, the effects of deuterium substitution on therate of metabolism have been reported for a very small percentage ofapproved drugs (see, e.g., Blake, M I et al, J Pharm Sci, 1975,64:367-91; Foster, A B, Adv Drug Res 1985, 14:1-40 (“Foster”); Kushner,D J et al, Can J Physiol Pharmacol 1999, 79-88; Fisher, M B et al, CurrOpin Drug Discov Devel, 2006, 9:101-09 (“Fisher”)). The results havebeen variable and unpredictable. For some compounds deuteration causeddecreased metabolic clearance in vivo. For others, there was no changein metabolism. Still others demonstrated increased metabolic clearance.The variability in deuterium effects has also led experts to question ordismiss deuterium modification as a viable drug design strategy forinhibiting adverse metabolism (see Foster at p. 35 and Fisher at p.101).

The effects of deuterium modification on a drug's metabolic propertiesare not predictable even when deuterium atoms are incorporated at knownsites of metabolism. Only by actually preparing and testing a deuterateddrug can one determine if and how the rate of metabolism will differfrom that of its non-deuterated counterpart. See, for example, Fukuto etal. (J. Med. Chem. 1991, 34, 2871-76). Many drugs have multiple siteswhere metabolism is possible. The site(s) where deuterium substitutionis required and the extent of deuteration necessary to see an effect onmetabolism, if any, will be different for each drug.

SUMMARY OF THE INVENTION

This invention relates to novel derivatives of idebenone. This inventionalso provides compositions comprising a compound of this invention andthe use of such compositions in methods of treating diseases such as aredescribed in U.S. Pat. Nos. 6,133,322, 4,436,753 and 5,059,627,including Friedreich's Ataxia; hypertrophic cardiomyopathy; ironoverload in Hallervorden-Spatz disease; sideroblastic anemia; ischemicdisease including, but not limited to, cerebral infarction, cerebralhemorrhage, cerebral hemorrhagic infarction, cerebral embolus, cardiacfailure, nephrosclerosis, proteinuria due to vascular lesion andrenovascular hypertension; degenerative nervous system disordersincluding, but not limited to, senile dementia and Alzheimer's disease;Duchenne's muscular dystrophy; multiple sclerosis, including primaryprogressive multiple sclerosis; and diseases or conditions that aretreatable by reducing oxidative toxicity in mitochondria. Idebenone hasbeen approved in several countries for Alzheimer's type dementia, and iscurrently undergoing clinical evaluation for Duchenne's musculardystrophy, MELAS syndrome (mitochondrial encephalopathy lactic acidosiswith stroke-like episodes), Leber's hereditary optic neuropathy, andFriedreich's ataxia. Idebenone is rapidly metabolized by oxidative chainshortening and its metabolites are reported to be inactive (Bodmer, M.,Eur J. Clin. Pharmacol. 65: 493-501 2009).

Despite the potential beneficial activities of idebenone, there is acontinuing need for new compounds to treat the aforementioned diseasesand conditions.

DEFINITIONS

The term “treat” means decrease, suppress, attenuate, diminish, arrest,or stabilize the development or progression of a disease (e.g., adisease or disorder delineated herein), lessen the severity of thedisease or improve the symptoms associated with the disease.

“Disease” means any condition or disorder that damages or interfereswith the normal function of a cell, tissue, or organ.

It will be recognized that some variation of natural isotopic abundanceoccurs in a synthesized compound depending upon the origin of chemicalmaterials used in the synthesis. Thus, a preparation of idebenone willinherently contain small amounts of deuterated isotopologues. Theconcentration of naturally abundant stable hydrogen and carbon isotope,notwithstanding this variation, is small and immaterial as compared tothe degree of stable isotopic substitution of compounds of thisinvention. See, for instance, Wada, E et al., Seikagaku, 1994, 66:15;Gannes, L Z et al., Comp Biochem Physiol Mol Integr Physiol, 1998,119:725.

In the compounds of this invention any atom not specifically designatedas a particular isotope is meant to represent any stable isotope of thatatom. Unless otherwise stated, when a position is designatedspecifically as “H” or “hydrogen”, the position is understood to havehydrogen at its natural abundance isotopic composition. Also unlessotherwise stated, when a position is designated specifically as “D” or“deuterium”, the position is understood to have deuterium at anabundance that is at least 3000 times greater than the natural abundanceof deuterium, which is 0.015% (i.e., at least 45% incorporation ofdeuterium).

The term “isotopic enrichment factor” as used herein means the ratiobetween the isotopic abundance and the natural abundance of a specifiedisotope.

In other embodiments, a compound of this invention has an isotopicenrichment factor for each designated deuterium atom of at least 3500(52.5% deuterium incorporation at each designated deuterium atom), atleast 4000 (60% deuterium incorporation), at least 4500 (67.5% deuteriumincorporation), at least 5000 (75% deuterium), at least 5500 (82.5%deuterium incorporation), at least 6000 (90% deuterium incorporation),at least 6333.3 (95% deuterium incorporation), at least 6466.7 (97%deuterium incorporation), at least 6600 (99% deuterium incorporation),or at least 6633.3 (99.5% deuterium incorporation).

The term “isotopologue” refers to a species in which the chemicalstructure differs from a specific compound of this invention only in theisotopic composition thereof.

The term “compound,” when referring to a compound of this invention,refers to a collection of molecules having an identical chemicalstructure, except that there may be isotopic variation among theconstituent atoms of the molecules. Thus, it will be clear to those ofskill in the art that a compound represented by a particular chemicalstructure containing indicated deuterium atoms, will also contain lesseramounts of isotopologues having hydrogen atoms at one or more of thedesignated deuterium positions in that structure. The relative amount ofsuch isotopologues in a compound of this invention will depend upon anumber of factors including the isotopic purity of deuterated reagentsused to make the compound and the efficiency of incorporation ofdeuterium in the various synthesis steps used to prepare the compound.However, as set forth above the relative amount of such isotopologues intoto will be less than 55% of the compound. In other embodiments, therelative amount of such isotopologues iii toto will be less than 50%,less than 47.5%, less than 40%, less than 32.5%, less than 25%, lessthan 17.5%, less than 10%, less than 5%, less than 3%, less than 1%, orless than 0.5% of the compound.

The invention also provides salts of the compounds of the invention.

A salt of a compound of this invention is formed between an acid and abasic group of the compound, such as an amino functional group, or abase and an acidic group of the compound, such as a carboxyl functionalgroup. According to another embodiment, the compound is apharmaceutically acceptable acid addition salt.

The term “pharmaceutically acceptable,” as used herein, refers to acomponent that is, within the scope of sound medical judgment, suitablefor use in contact with the tissues of humans and other mammals withoutundue toxicity, irritation, allergic response and the like, and arecommensurate with a reasonable benefit/risk ratio. A “pharmaceuticallyacceptable salt” means any non-toxic salt that, upon administration to arecipient, is capable of providing, either directly or indirectly, acompound of this invention. A “pharmaceutically acceptable counterion”is an ionic portion of a salt that is not toxic when released from thesalt upon administration to a recipient.

The pharmaceutically acceptable salt may also be a salt of a compound ofthe present invention and a base. Exemplary bases include, but are notlimited to, hydroxide of alkali metals including sodium, potassium, andlithium; hydroxides of alkaline earth metals such as calcium andmagnesium; hydroxides of other metals, such as aluminum and zinc;ammonia, organic amines such as unsubstituted or hydroxyl-substitutedmono-, di-, or tri-alkylamines, dicyclohexylamine; tributyl amine;pyridine; N-methylamine, N-ethylamine; diethylamine; triethylamine;mono-, bis-, or tris-(2-OH—(C₁-C₆)-alkylamine), such asN,N-dimethyl-N-(2-hydroxyethyl)amine or tri-(2-hydroxyethyl)amine;N-methyl-D-glucamine; morpholine; thiomorpholine; piperidine;pyrrolidine; and amino acids such as arginine, lysine, and the like.

The compounds of the present invention (e.g., compounds of Formula I),may contain an asymmetric carbon atom, for example, as the result ofdeuterium substitution or otherwise. As such, compounds of thisinvention can exist as either individual enantiomers, or mixtures of thetwo enantiomers. Accordingly, a compound of the present invention mayexist as either a racemic mixture or a scalemic mixture, or asindividual respective stereoisomers that are substantially free fromanother possible stereoisomer. The term “substantially free of otherstereoisomers” as used herein means less than 25% of otherstereoisomers, preferably less than 10% of other stereoisomers, morepreferably less than 5% of other stereoisomers and most preferably lessthan 2% of other stereoisomers are present. Methods of obtaining orsynthesizing an individual enantiomer for a given compound are known inthe art and may be applied as practicable to final compounds or tostarting material or intermediates.

Unless otherwise indicated, when a disclosed compound is named ordepicted by a structure without specifying the stereochemistry and hasone or more chiral centers, it is understood to represent all possiblestereoisomers of the compound.

The term “stable compounds,” as used herein, refers to compounds whichpossess stability sufficient to allow for their manufacture and whichmaintain the integrity of the compound for a sufficient period of timeto be useful for the purposes detailed herein (e.g., formulation intotherapeutic products, intermediates for use in production of therapeuticcompounds, isolatable or storable intermediate compounds, treating adisease or condition responsive to therapeutic agents).

“D” and “d” both refer to deuterium. “d_(x-y)” refers to substitutionwith from x to y number of deuterium atoms. “Stereoisomer” refers toboth enantiomers and diastereomers. “Tert” and “t-” each refer totertiary. “US” refers to the United States of America.

A group is “substituted with” a substituent when one or more hydrogenatoms of the group are replaced with a corresponding number ofsubstituent atoms (if the substituent is an atom) or groups (if thesubstituent is a group). For example, “substituted with deuterium”refers to the replacement of one or more hydrogen atoms with acorresponding number of deuterium atoms.

Throughout this specification, a variable may be referred to generally(e.g., “each Y”) or may be referred to specifically (e.g., Y¹, Y², Y³,etc.). Unless otherwise indicated, when a variable is referred togenerally, it is meant to include all specific embodiments of thatparticular variable.

Therapeutic Compounds

The present invention in one embodiment provides a compound of FormulaI:

or a pharmaceutically acceptable salt thereof, wherein:

-   -   each of R¹, R² and R³ is independently selected from CH₃, CH₂D,        CHD₂ and CD₃;    -   each Y¹ is the same and is hydrogen or deuterium;    -   each Y² is the same and is hydrogen or deuterium;    -   each Y³ is the same and is hydrogen or deuterium;    -   each Y⁴ is the same and is hydrogen or deuterium;    -   each Y⁵ is the same and is hydrogen or deuterium;    -   each Y⁶ is the same and is hydrogen or deuterium;    -   each Y⁷ is the same and is hydrogen or deuterium;    -   each Y⁸ is the same and is hydrogen or deuterium;    -   each Y⁹ is the same and is hydrogen or deuterium; and    -   each Y¹⁰ is the same and is hydrogen or deuterium;        provided that if each Y¹ is hydrogen; each Y² is hydrogen; each        Y³ is hydrogen; each Y⁴ is hydrogen; each Y⁵ is hydrogen; each        Y⁶ is hydrogen; each Y⁷ is hydrogen; each Y⁸ is hydrogen; each        Y⁹ is hydrogen; each Y¹⁰ is hydrogen; R² is CH₃; and R³ is CH₃;        then R¹ is CH₂D or CHD₂.

In one set of embodiments of the compound of Formula I, each of R¹, R³and R² is independently selected from CH₃ and CD₃.

In one embodiment of the compound of Formula I, each Y¹⁰ is deuterium.In one aspect of this embodiment, each Y⁹ is hydrogen. In another aspectof this embodiment, each Y⁹ is deuterium. In one aspect of thisembodiment, each Y⁸ is hydrogen. In another aspect of this embodiment,each Y⁸ is deuterium. In one aspect of this embodiment, R¹ is CH₃. Inanother aspect of this embodiment, R¹ is CD₃. In another aspect of thisembodiment, R² is CH₃. In another aspect of this embodiment, R² is CD₃.In one aspect of this embodiment, R³ is CH₃. In another aspect of thisembodiment, R³ is CD₃.

In one embodiment of the compound of Formula I, each Y¹⁰ is hydrogen. Inone aspect of this embodiment, each Y⁹ is hydrogen. In another aspect ofthis embodiment, each Y⁹ is deuterium. In one aspect of this embodiment,each Y⁸ is hydrogen. In another aspect of this embodiment, each Y⁸ isdeuterium. In one aspect of this embodiment, R¹ is CH₃. In anotheraspect of this embodiment, R¹ is CD₃. In another aspect of thisembodiment, R² is CH₃. In another aspect of this embodiment, R² is CD₃.In one aspect of this embodiment, R³ is CH₃. In another aspect of thisembodiment, R³ is CD₃.

In one embodiment of the compound of Formula I, each Y⁹ is deuterium. Inone aspect of this embodiment, each Y⁸ is hydrogen. In another aspect ofthis embodiment, each Y⁸ is deuterium. In one aspect of this embodiment,R¹ is CH₃. In another aspect of this embodiment, R¹ is CD₃. In anotheraspect of this embodiment, R² is CH₃. In another aspect of thisembodiment, R² is CD₃. In one aspect of this embodiment, R³ is CH₃. Inanother aspect of this embodiment, R³ is CD₃.

In one embodiment of the compound of Formula I, each Y⁹ is hydrogen. Inone aspect of this embodiment, each Y⁸ is hydrogen. In another aspect ofthis embodiment, each Y⁸ is deuterium. In one aspect of this embodiment,R¹ is CH₃. In another aspect of this embodiment, R¹ is CD₃. In anotheraspect of this embodiment, R² is CH₃. In another aspect of thisembodiment, R² is CD₃. In one aspect of this embodiment, R³ is CH₃. Inanother aspect of this embodiment, R³ is CD₃.

In one embodiment, each Y¹ is deuterium; each Y² is deuterium; each Y³is deuterium; each Y⁴ is deuterium; each Y¹ is deuterium; each Y⁶ isdeuterium; each Y⁷ is deuterium; each Y⁸ is deuterium; each Y⁹ isdeuterium; and each Y¹⁰ is deuterium.

In one embodiment, each Y¹, each Y² and each Y³ are all hydrogen. In oneembodiment, each Y¹, each Y² and each Y³ are all deuterium.

In yet another embodiment, the compound is selected from any one of thecompounds (Cmpd) set forth in Table 1 (below), wherein each Y¹ ishydrogen; each Y² is hydrogen; each Y³ is hydrogen; each Y⁴ is hydrogen;each Y⁵ is hydrogen; each Y⁶ is hydrogen; each Y⁷ is hydrogen; and R³ isCH₃:

TABLE 1 Exemplary Embodiments of Formula I Cmpd No. R¹ R² each Y¹⁰ eachY⁹ each Y⁸ 101 CH₃ CH₃ H H D 102 CH₃ CH₃ H D H 103 CH₃ CH₃ H D D 104 CH₃CH₃ D H H 105 CH₃ CH₃ D H D 106 CH₃ CH₃ D D H 107 CH₃ CH₃ D D D 108 CH₃CD₃ H H H 109 CH₃ CD₃ H H D 110 CH₃ CD₃ H D H 111 CH₃ CD₃ H D D 112 CH₃CD₃ D H H 113 CH₃ CD₃ D H D 114 CH₃ CD₃ D D H 115 CH₃ CD₃ D D D 117 CD₃CH₃ H H D 118 CD₃ CH₃ H D H 119 CD₃ CH₃ H D D 120 CD₃ CH₃ D H H 121 CD₃CH₃ D H D 122 CD₃ CH₃ D D H 123 CD₃ CH₃ D D D 124 CD₃ CD₃ H H H 125 CD₃CD₃ H H D 126 CD₃ CD₃ H D H 127 CD₃ CD₃ H D D 128 CD₃ CD₃ D H H 129 CD₃CD₃ D H D 130 CD₃ CD₃ D D H 131 CD₃ CD₃ D D Dor a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.

In yet another embodiment, the compound is selected from any one of thecompounds (Cmpd) set forth in Table 2 (below), wherein each Y¹ ishydrogen; each Y² is hydrogen; each Y³ is hydrogen; each Y⁴ is hydrogen;each Y⁵ is hydrogen; each Y⁶ is hydrogen; each Y⁷ is hydrogen; and R³ isCD₃:

TABLE 2 Exemplary Embodiments of Formula I Cmpd No. R¹ R² each Y¹⁰ eachY⁹ each Y⁸ 200 CH₃ CH₃ H H H 201 CH₃ CH₃ H H D 202 CH₃ CH₃ H D H 203 CH₃CH₃ H D D 204 CH₃ CH₃ D H H 205 CH₃ CH₃ D H D 206 CH₃ CH₃ D D H 207 CH₃CH₃ D D D 208 CH₃ CD₃ H H H 209 CH₃ CD₃ H H D 210 CH₃ CD₃ H D H 211 CH₃CD₃ H D D 212 CH₃ CD₃ D H H 213 CH₃ CD₃ D H D 214 CH₃ CD₃ D D H 215 CH₃CD₃ D D D 216 CD₃ CH₃ H H H 217 CD₃ CH₃ H H D 218 CD₃ CH₃ H D H 219 CD₃CH₃ H D D 220 CD₃ CH₃ D H H 221 CD₃ CH₃ D H D 222 CD₃ CH₃ D D H 223 CD₃CH₃ D D D 224 CD₃ CD₃ H H H 225 CD₃ CD₃ H H D 226 CD₃ CD₃ H D H 227 CD₃CD₃ H D D 228 CD₃ CD₃ D H H 229 CD₃ CD₃ D H D 230 CD₃ CD₃ D D H 231 CD₃CD₃ D D Dor a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.

In yet another embodiment, the compound is selected from any one of thecompounds (Cmpd) set forth in Table 3 below, wherein each Y¹ isdeuterium; each Y² is deuterium; each Y³ is deuterium; each Y⁴ isdeuterium; each Y⁵ is deuterium; each Y⁶ is deuterium; each Y⁷ isdeuterium; each Y⁸ is deuterium; each Y⁹ is deuterium; and each Y¹⁰ isdeuterium:

TABLE 3 Exemplary Embodiments of Formula I Cmpd No. R¹ R² R³ 300 CH₃ CH₃CH₃ 301 CH₃ CH₃ CD₃ 302 CH₃ CD₃ CH₃ 303 CH₃ CD₃ CD₃ 304 CD₃ CH₃ CH₃ 305CD₃ CH₃ CD₃ 306 CD₃ CD₃ CH₃ 307 CD₃ CD₃ CD₃or a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.

In another set of embodiments, any atom not designated as deuterium inany of the embodiments, aspects, or examples set forth above is presentat its natural isotopic abundance.

The synthesis of compounds of Formula I may be readily achieved bysynthetic chemists of ordinary skill by reference to the ExemplarySynthesis and Examples disclosed herein. Relevant procedures analogousto those of use for the preparation of compounds of Formula I andintermediates thereof are disclosed, for instance in U.S. Pat. No.4,139,545.

Such methods can be carried out utilizing corresponding deuterated andoptionally, other isotope-containing reagents and/or intermediates tosynthesize the compounds delineated herein, or invoking standardsynthetic protocols known in the art for introducing isotopic atoms to achemical structure.

Exemplary Synthesis

Scheme 1 provides an exemplary procedure for the preparation of thecompounds of Formula I.

The compounds of Formula I may be prepared in a manner analogous to thatdescribed by Tsoukala, A. et al., Org Process Res. Dev (2011), 15:673-680. Starting material 10 is converted to 11 in the presence ofKBr/acid. Coupling of 11 with 12 using Pd(PPh₃)₄ as catalyst yields amixture of 13a and 13b. Reduction of the alkene bond with either H₂ orD₂ as described in Scheme 1 leads to 14 which is then converted to acompound of Formula I via oxidation and subsequent deprotection.

Starting compound 10a, wherein R³ is CD₃, may be prepared as describedby Hamamura, K. et al., J of Labeled Compounds and Radiopharmaceuticals(2002), 45(10): 831-839,

Appropriately deuterated intermediates 12, may be prepared as shown inScheme 2a or Scheme 2b, below.

Using methods well known in the arts, appropriately deuterated diol 15is first protected as the mono-TBS ether, then treated with the Burgessreagent to yield intermediates 12.

Starting diol 15a is commercially available,

Using routine methods in the arts, appropriately deuterated diol 16 isfirst protected as the mono-TBS ether, then treated with mesyl chlorideprior to coupling with appropriately deuterated Grignard reagent 17 toyield intermediates 12.

Starting diols 16a and 16b are commercially available,

Starting diol 16c may be prepared by treating diethyl malonate withLiAlD₄ as described by Dickschat, J. S. et al., Eur. J of Org Chem.,(2011), 18: 3339-3346,

The specific approaches and compounds shown above are not intended to belimiting. The chemical structures in the schemes herein depict variablesthat are hereby defined commensurately with chemical group definitions(moieties, atoms, etc.) of the corresponding position in the compoundformulae herein, whether identified by the same variable name (i.e., R¹,R², R³, etc.) or not. The suitability of a chemical group in a compoundstructure for use in the synthesis of another compound is within theknowledge of one of ordinary skill in the art.

Additional methods of synthesizing compounds of Formula I and theirsynthetic precursors, including those within routes not explicitly shownin schemes herein, are within the means of chemists of ordinary skill inthe art. Synthetic chemistry transformations and protecting groupmethodologies (protection and deprotection) useful in synthesizing theapplicable compounds are known in the art and include, for example,those described in Larock R, Comprehensive Organic Transformations, VCHPublishers (1989); Greene, T W et al., Protective Groups in OrganicSynthesis, 3^(rd) Ed., John Wiley and Sons (1999); Fieser, L et al.,Fieser and Fieser's Reagents for Organic Synthesis, John Wiley and Sons(1994); and Paquette, L, ed., Encyclopedia of Reagents for OrganicSynthesis, John Wiley and Sons (1995) and subsequent editions thereof.

Combinations of substituents and variables envisioned by this inventionare only those that result in the formation of stable compounds.

Compositions

The invention also provides pharmaceutical compositions comprising aneffective amount of a compound of Formula I or pharmaceuticallyacceptable salt thereof, or a pharmaceutically acceptable salt of saidcompound; and a pharmaceutically acceptable carrier.

The invention also provides pharmaceutical compositions comprising aneffective amount of a compound of Formula II:

wherein:

-   -   each of R², R³ and R⁴ is independently selected from CH₃, CH₂D,        CHD₂ and CD₃;    -   each Y¹ is the same and is hydrogen or deuterium;    -   each Y² is the same and is hydrogen or deuterium;    -   each Y³ is the same and is hydrogen or deuterium;    -   each Y⁴ is the same and is hydrogen or deuterium;    -   each Y⁵ is the same and is hydrogen or deuterium;    -   each Y⁶ is the same and is hydrogen or deuterium;    -   each Y⁷ is the same and is hydrogen or deuterium;    -   each Y⁸ is the same and is hydrogen or deuterium;    -   each Y⁹ is the same and is hydrogen or deuterium; and    -   each Y¹⁰ is the same and is hydrogen or deuterium;        provided that if each Y¹ is hydrogen; each Y² is hydrogen; each        Y³ is hydrogen; each Y⁴ is hydrogen; each Y⁵ is hydrogen; each        Y⁶ is hydrogen; each Y⁷ is hydrogen; each Y⁸ is hydrogen; each        Y⁹ is hydrogen; each Y¹⁰ is hydrogen; R² is CH₃; and R³ is CH₃;        then R⁴ is not CH₃;        or a pharmaceutically acceptable salt of said compound; and a        pharmaceutically acceptable carrier.

In one embodiment, the compound of Formula II is compound 116:

or a pharmaceutically acceptable salt thereof.The carrier(s) are “acceptable” in the sense of being compatible withthe other ingredients of the formulation and, in the case of apharmaceutically acceptable carrier, not deleterious to the recipientthereof in an amount used in the medicament.

Pharmaceutically acceptable carriers, adjuvants and vehicles that may beused in the pharmaceutical compositions of this invention include, butare not limited to, ion exchangers, alumina, aluminum stearate,lecithin, serum proteins, such as human serum albumin, buffer substancessuch as phosphates, glycine, sorbic acid, potassium sorbate, partialglyceride mixtures of saturated vegetable fatty acids, water, salts orelectrolytes, such as protamine sulfate, disodium hydrogen phosphate,potassium hydrogen phosphate, sodium chloride, zinc salts, colloidalsilica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-basedsubstances, polyethylene glycol, sodium carboxymethylcellulose,polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers,polyethylene glycol and wool fat.

If required, the solubility and bioavailability of the compounds of thepresent invention in pharmaceutical compositions may be enhanced bymethods well-known in the art. One method includes the use of lipidexcipients in the formulation. See “Oral Lipid-Based Formulations:Enhancing the Bioavailability of Poorly Water-Soluble Drugs (Drugs andthe Pharmaceutical Sciences),” David J. Hauss, ed. Informa Healthcare,2007; and “Role of Lipid Excipients in Modifying Oral and ParenteralDrug Delivery: Basic Principles and Biological Examples,” Kishor M.Wasan, ed. Wiley-Interscience, 2006.

Another known method of enhancing bioavailability is the use of anamorphous form of a compound of this invention optionally formulatedwith a poloxamer, such as LUTROL™ and PLURONIC™ (BASF Corporation), orblock copolymers of ethylene oxide and propylene oxide. See U.S. Pat.No. 7,014,866; and United States patent publications 20060094744 and20060079502.

The pharmaceutical compositions of the invention include those suitablefor oral, rectal, nasal, topical (including buccal and sublingual),vaginal or parenteral (including subcutaneous, intramuscular,intravenous and intradermal) administration. In certain embodiments, thecompound of the formulae herein is administered transdermally (e.g.,using a transdermal patch or iontophoretic techniques). Otherformulations may conveniently be presented in unit dosage form, e.g.,tablets, sustained release capsules, and in liposomes, and may beprepared by any methods well known in the art of pharmacy. See, forexample, Remington: The Science and Practice of Pharmacy, LippincottWilliams & Wilkins, Baltimore, Md. (20th ed. 2000).

Such preparative methods include the step of bringing into associationwith the molecule to be administered ingredients such as the carrierthat constitutes one or more accessory ingredients. In general, thecompositions are prepared by uniformly and intimately bringing intoassociation the active ingredients with liquid carriers, liposomes orfinely divided solid carriers, or both, and then, if necessary, shapingthe product.

In certain embodiments, the compound is administered orally.Compositions of the present invention suitable for oral administrationmay be presented as discrete units such as capsules, sachets, or tabletseach containing a predetermined amount of the active ingredient; apowder or granules; a solution or a suspension in an aqueous liquid or anon-aqueous liquid; an oil-in-water liquid emulsion; a water-in-oilliquid emulsion; packed in liposomes; or as a bolus, etc. Soft gelatincapsules can be useful for containing such suspensions, which maybeneficially increase the rate of compound absorption.

In the case of tablets for oral use, carriers that are commonly usedinclude lactose and corn starch. Lubricating agents, such as magnesiumstearate, are also typically added. For oral administration in a capsuleform, useful diluents include lactose and dried cornstarch. When aqueoussuspensions are administered orally, the active ingredient is combinedwith emulsifying and suspending agents. If desired, certain sweeteningand/or flavoring and/or coloring agents may be added.

Compositions suitable for oral administration include lozengescomprising the ingredients in a flavored basis, usually sucrose andacacia or tragacanth; and pastilles comprising the active ingredient inan inert basis such as gelatin and glycerin, or sucrose and acacia.

Compositions suitable for parenteral administration include aqueous andnon-aqueous sterile injection solutions which may contain anti-oxidants,buffers, bacteriostats and solutes which render the formulation isotonicwith the blood of the intended recipient; and aqueous and non-aqueoussterile suspensions which may include suspending agents and thickeningagents. The formulations may be presented in unit-dose or multi-dosecontainers, for example, sealed ampules and vials, and may be stored ina freeze dried (lyophilized) condition requiring only the addition ofthe sterile liquid carrier, for example water for injections,immediately prior to use. Extemporaneous injection solutions andsuspensions may be prepared from sterile powders, granules and tablets.

Such injection solutions may be in the form, for example, of a sterileinjectable aqueous or oleaginous suspension. This suspension may beformulated according to techniques known in the art using suitabledispersing or wetting agents (such as, for example, Tween 80) andsuspending agents. The sterile injectable preparation may also be asterile injectable solution or suspension in a non-toxicparenterally-acceptable diluent or solvent, for example, as a solutionin 1,3-butanediol. Among the acceptable vehicles and solvents that maybe employed are mannitol, water, Ringer's solution and isotonic sodiumchloride solution. In addition, sterile, fixed oils are conventionallyemployed as a solvent or suspending medium. For this purpose, any blandfixed oil may be employed including synthetic mono- or diglycerides.Fatty acids, such as oleic acid and its glyceride derivatives are usefulin the preparation of injectables, as are naturalpharmaceutically-acceptable oils, such as olive oil or castor oil,especially in their polyoxyethylated versions. These oil solutions orsuspensions may also contain a long-chain alcohol diluent or dispersant.

The pharmaceutical compositions of this invention may be administered inthe form of suppositories for rectal administration. These compositionscan be prepared by mixing a compound of this invention with a suitablenon-irritating excipient which is solid at room temperature but liquidat the rectal temperature and therefore will melt in the rectum torelease the active components. Such materials include, but are notlimited to, cocoa butter, beeswax and polyethylene glycols.

The pharmaceutical compositions of this invention may be administered bynasal aerosol or inhalation. Such compositions are prepared according totechniques well-known in the art of pharmaceutical formulation and maybe prepared as solutions in saline, employing benzyl alcohol or othersuitable preservatives, absorption promoters to enhance bioavailability,fluorocarbons, and/or other solubilizing or dispersing agents known inthe art. See, e.g.: Rabinowitz J D and Zaffaroni A C, U.S. Pat. No.6,803,031, assigned to Alexza Molecular Delivery Corporation.

Topical administration of the pharmaceutical compositions of thisinvention is especially useful when the desired treatment involves areasor organs readily accessible by topical application. For topicalapplication topically to the skin, the pharmaceutical composition shouldbe formulated with a suitable ointment containing the active componentssuspended or dissolved in a carrier. Carriers for topical administrationof the compounds of this invention include, but are not limited to,mineral oil, liquid petroleum, white petroleum, propylene glycol,polyoxyethylene polyoxypropylene compound, emulsifying wax, and water.Alternatively, the pharmaceutical composition can be formulated with asuitable lotion or cream containing the active compound suspended ordissolved in a carrier. Suitable carriers include, but are not limitedto, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esterswax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol, and water. Thepharmaceutical compositions of this invention may also be topicallyapplied to the lower intestinal tract by rectal suppository formulationor in a suitable enema formulation. Topically-transdermal patches andiontophoretic administration are also included in this invention.

Application of the subject therapeutics may be local, so as to beadministered at the site of interest. Various techniques can be used forproviding the subject compositions at the site of interest, such asinjection, use of catheters, trocars, projectiles, pluronic gel, stents,sustained drug release polymers or other device which provides forinternal access.

Thus, according to yet another embodiment, the compounds of thisinvention may be incorporated into compositions for coating animplantable medical device, such as prostheses, artificial valves,vascular grafts, stents, or catheters. Suitable coatings and the generalpreparation of coated implantable devices are known in the art and areexemplified in U.S. Pat. Nos. 6,099,562; 5,886,026; and 5,304,121. Thecoatings are typically biocompatible polymeric materials such as ahydrogel polymer, polymethyldisiloxane, polycaprolactone, polyethyleneglycol, polylactic acid, ethylene vinyl acetate, and mixtures thereof.The coatings may optionally be further covered by a suitable topcoat offluorosilicone, polysaccharides, polyethylene glycol, phospholipids orcombinations thereof to impart controlled release characteristics in thecomposition. Coatings for invasive devices are to be included within thedefinition of pharmaceutically acceptable carrier, adjuvant or vehicle,as those terms are used herein.

According to another embodiment, the invention provides a method ofcoating an implantable medical device comprising the step of contactingsaid device with the coating composition described above. It will beobvious to those skilled in the art that the coating of the device willoccur prior to implantation into a mammal.

According to another embodiment, the invention provides a method ofimpregnating an implantable drug release device comprising the step ofcontacting said drug release device with a compound or composition ofthis invention. Implantable drug release devices include, but are notlimited to, biodegradable polymer capsules or bullets, non-degradable,diffusible polymer capsules and biodegradable polymer wafers.

According to another embodiment, the invention provides an implantablemedical device coated with a compound or a composition comprising acompound of this invention, such that said compound is therapeuticallyactive.

According to another embodiment, the invention provides an implantabledrug release device impregnated with or containing a compound or acomposition comprising a compound of this invention, such that saidcompound is released from said device and is therapeutically active.

Where an organ or tissue is accessible because of removal from thesubject, such organ or tissue may be bathed in a medium containing acomposition of this invention, a composition of this invention may bepainted onto the organ, or a composition of this invention may beapplied in any other convenient way.

In another embodiment, a composition of this invention further comprisesa second therapeutic agent. The second therapeutic agent may be selectedfrom any compound or therapeutic agent known to have or thatdemonstrates advantageous properties when administered with a compoundhaving the same mechanism of action as idebenone. Such agents includethose indicated as being useful in combination with idebenone, includingbut not limited to, donepezil, zanapezil, tacrine, ipiacrine,rivastigmine, T-588, TAK-147 and xaliproden (described in U.S. Pat. No.5,962,535 and U.S. Pat. No. 7,342,043).

In another embodiment, the invention provides separate dosage forms of acompound of this invention and one or more of any of the above-describedsecond therapeutic agents, wherein the compound and second therapeuticagent are associated with one another. The term “associated with oneanother” as used herein means that the separate dosage forms arepackaged together or otherwise attached to one another such that it isreadily apparent that the separate dosage forms are intended to be soldand administered together (within less than 24 hours of one another,consecutively or simultaneously).

In the pharmaceutical compositions of the invention, the compound of thepresent invention is present in an effective amount. As used herein, theterm “effective amount” refers to an amount which, when administered ina proper dosing regimen, is sufficient to treat the target disorder.

The interrelationship of dosages for animals and humans (based onmilligrams per meter squared of body surface) is described in Freireichet al., Cancer Chemother. Rep, 1966, 50: 219. Body surface area may beapproximately determined from height and weight of the subject. See,e.g., Scientific Tables, Geigy Pharmaceuticals, Ardsley, N.Y., 1970,537.

In one embodiment, an effective amount of a compound of this inventioncan range from 1 mg/kg to 50 mg/kg, administered once a day, such as 2.5mg to 50 mg/kg, administered once a day, such as 2.5 mg to 25 mg/kg,administered once a day, such as 5 mg to 25 mg/kg, administered once aday.

In one embodiment, an effective amount of a compound of this inventioncan range from 1 mg/kg to 50 mg/kg, administered twice a day, such as2.5 mg to 50 mg/kg, administered twice a day, such as 2.5 mg to 25mg/kg, administered twice a day, such as 5 mg to 25 mg/kg, administeredtwice a day.

In one embodiment, an effective amount of a compound of this inventioncan range from 50 mg to 5000 mg, such as 100 mg to 2500 mg, such as 100mg to 2250 mg, such as 150 mg to 2250 mg, such as 180 mg to 2250 mg.which can be administered once a day.

Effective doses will also vary, as recognized by those skilled in theart, depending on the diseases treated, the severity of the disease, theroute of administration, the sex, age and general health condition ofthe subject, excipient usage, the possibility of co-usage with othertherapeutic treatments such as use of other agents and the judgment ofthe treating physician.

For pharmaceutical compositions that comprise a second therapeuticagent, an effective amount of the second therapeutic agent is betweenabout 20% and 100% of the dosage normally utilized in a monotherapyregime using just that agent. Preferably, an effective amount is betweenabout 70% and 100% of the normal monotherapeutic dose. The normalmonotherapeutic dosages of these second therapeutic agents are wellknown in the art. See, e.g., Wells et al., eds., PharmacotherapyHandbook, 2nd Edition, Appleton and Lange, Stamford, Conn. (2000); PDRPharmacopoeia, Tarascon Pocket Pharmacopoeia 2000, Deluxe Edition,Tarascon Publishing, Loma Linda, Calif. (2000), each of which referencesare incorporated herein by reference in their entirety.

It is expected that some of the second therapeutic agents referencedabove will act synergistically with the compounds of this invention.When this occurs, it will allow the effective dosage of the secondtherapeutic agent and/or the compound of this invention to be reducedfrom that required in a monotherapy. This has the advantage ofMinimizing toxic side effects of either the second therapeutic agent ofa compound of this invention, synergistic improvements in efficacy,improved ease of administration or use and/or reduced overall expense ofcompound preparation or formulation.

Methods of Treatment

In another embodiment, the invention provides a method of reducingoxidative toxicity in mitochondria, comprising contacting mitochondriawith one or more compounds of Formula I or Formula II herein.

According to another embodiment, the invention provides a method oftreating diseases such as are described in U.S. Pat. Nos. 6,133,322,4,436,753 and 5,059,627, including Friedreich's Ataxia; hypertrophiccardiomyopathy; iron overload in Hallervorden-Spatz disease;sideroblastic anemia; ischemic disease including, but not limited to,cerebral infarction, cerebral hemorrhage, cerebral hemorrhagicinfarction, cerebral embolus, cardiac failure, nephrosclerosis,proteinuria due to vascular lesion and renovascular hypertension;degenerative nervous system disorders including, but not limited to,senile dementia and Alzheimer's disease; Duchenne's muscular dystrophy;and multiple sclerosis, including primary progressive multiplesclerosis. In one embodiment, the disease is Duchenne's musculardystrophy; or multiple sclerosis, including primary progressive multiplesclerosis.

According to one embodiment, the invention provides a method of treatingAlzheimer's type dementia, Duchenne's muscular dystrophy, MELAS syndrome(mitochondrial encephalopathy lactic acidosis with stroke-likeepisodes), Leber's hereditary optic neuropathy, and Friedreich's ataxia.

Identifying a subject in need of such treatment can be in the judgmentof a subject or a health care professional and can be subjective (e.g.opinion) or objective (e.g. measurable by a test or diagnostic method).In one embodiment the subject is a patient.

In another embodiment, any of the above methods of treatment comprisesthe further step of co-administering to the subject in need thereof oneor more second therapeutic agents. The choice of second therapeuticagent may be made from any second therapeutic agent known to be usefulfor co-administration with idebenone. The choice of second therapeuticagent is also dependent upon the particular disease or condition to betreated. Examples of second therapeutic agents that may be employed inthe methods of this invention are those set forth above for use incombination compositions comprising a compound of this invention and asecond therapeutic agent. Such agents include but are not limited todonepezil, zanapezil, tacrine, ipiacrine, rivastigmine, T-588, TAK-147and xaliproden (described in U.S. Pat. No. 5,962,535 and U.S. Pat. No.7,342,043).

The term “co-administered” as used herein means that the secondtherapeutic agent may be administered together with a compound of thisinvention as part of a single dosage form (such as a composition of thisinvention comprising a compound of the invention and an secondtherapeutic agent as described above) or as separate, multiple dosageforms. Alternatively, the additional agent may be administered prior to,consecutively with, or following the administration of a compound ofthis invention. In such combination therapy treatment, both thecompounds of this invention and the second therapeutic agent(s) areadministered by conventional methods. The administration of acomposition of this invention, comprising both a compound of theinvention and a second therapeutic agent, to a subject does not precludethe separate administration of that same therapeutic agent, any othersecond therapeutic agent or any compound of this invention to saidsubject at another time during a course of treatment.

Effective amounts of these second therapeutic agents are well known tothose skilled in the art and guidance for dosing may be found in patentsand published patent applications referenced herein, as well as in Wellset al., eds., Pharmacotherapy Handbook, 2nd Edition, Appleton and Lange,Stamford, Conn. (2000); PDR Pharmacopoeia, Tarascon Pocket Pharmacopoeia2000, Deluxe Edition, Tarascon Publishing, Loma Linda, Calif. (2000),and other medical texts. However, it is well within the skilledartisan's purview to determine the second therapeutic agent's optimaleffective-amount range.

In one embodiment of the invention, where a second therapeutic agent isadministered to a subject, the effective amount of the compound of thisinvention is less than its effective amount would be where the secondtherapeutic agent is not administered. In another embodiment, theeffective amount of the second therapeutic agent is less than itseffective amount would be where the compound of this invention is notadministered. In this way, undesired side effects associated with highdoses of either agent may be minimized. Other potential advantages(including without limitation improved dosing regimens and/or reduceddrug cost) will be apparent to those of skill in the art.

In yet another aspect, the invention provides the use of a compound ofFormula I or Formula II alone or together with one or more of theabove-described second therapeutic agents in the manufacture of amedicament, either as a single composition or as separate dosage forms,for treatment or prevention in a subject of a disease, disorder orsymptom set forth above. Another aspect of the invention is a compoundof Formula I or Formula II for use in the treatment or prevention in asubject of a disease, disorder or symptom thereof delineated herein.

Example 1 Evaluation of Metabolic Stability

Microsomal Assay:

Human liver microsomes (20 mg/mL) are obtained from Xenotech, LLC(Lenexa, Kans.). β-nicotinamide adenine dinucleotide phosphate, reducedform (NADPH), magnesium chloride (MgCl₂), and dimethyl sulfoxide (DMSO)are purchased from Sigma-Aldrich.

Determination of Metabolic Stability:

7.5 mM stock solutions of test compounds are prepared in DMSO. The 7.5mM stock solutions are diluted to 12.5-50 μM in acetonitrile (ACN). The20 mg/mL human liver microsomes are diluted to 0.625 mg/mL in 0.1 Mpotassium phosphate buffer, pH 7.4, containing 3 mM MgCl₂. The dilutedmicrosomes are added to wells of a 96-well deep-well polypropylene platein triplicate. A 10 μL aliquot of the 12.5-50 μM test compound is addedto the microsomes and the mixture is pre-warmed for 10 minutes.Reactions are initiated by addition of pre-warmed NADPH solution. Thefinal reaction volume is 0.5 mL and contains 0.5 mg/mL human livermicrosomes, 0.25-1.0 μM test compound, and 2 mM NADPH in 0.1 M potassiumphosphate buffer, pH 7.4, and 3 mM MgCl₂. The reaction mixtures areincubated at 37° C., and 50 μL aliquots are removed at 0, 5, 10, 20, and30 minutes and added to shallow-well 96-well plates which contain 504 ofice-cold ACN with internal standard to stop the reactions. The platesare stored at 4° C. for 20 minutes after which 100 μL of water is addedto the wells of the plate before centrifugation to pellet precipitatedproteins. Supernatants are transferred to another 96-well plate andanalyzed for amounts of parent remaining by LC-MS/MS using an AppliedBio-systems API 4000 mass spectrometer. The same procedure is followedfor the non-deuterated counterpart of the compound of Formula I orFormula II and the positive control, 7-ethoxycoumarin (1 μM). Testing isdone in triplicate.

Data Analysis:

The in vitro t_(1/2)s for test compounds are calculated from the slopesof the linear regression of % parent remaining (ln) vs incubation timerelationship.

in vitro t _(1/2)=0.693/k

k=−[slope of linear regression of % parent remaining(ln)vs incubationtime]

Data analysis is performed using Microsoft Excel Software.

Without further description, it is believed that one of ordinary skillin the art can, using the preceding description and the illustrativeexamples, make and utilize the compounds of the present invention andpractice the claimed methods. It should be understood that the foregoingdiscussion and examples merely present a detailed description of certainpreferred embodiments. It will be apparent to those of ordinary skill inthe art that various modifications and equivalents can be made withoutdeparting from the spirit and scope of the invention.

1. A compound of Formula I:

or a pharmaceutically acceptable salt thereof, wherein: each of R¹, R²and R³ is independently selected from CH₃, CH₂D, CHD₂ and CD₃; each Y¹is the same and is hydrogen or deuterium; each Y² is the same and ishydrogen or deuterium; each Y³ is the same and is hydrogen or deuterium;each Y⁴ is the same and is hydrogen or deuterium; each Y⁵ is the sameand is hydrogen or deuterium; each Y⁶ is the same and is hydrogen ordeuterium; each Y⁷ is the same and is hydrogen or deuterium; each Y⁸ isthe same and is hydrogen or deuterium; each Y⁹ is the same and ishydrogen or deuterium; and each Y¹⁰ is the same and is hydrogen ordeuterium; provided that if each Y¹ is hydrogen; each Y² is hydrogen;each Y³ is hydrogen; each Y⁴ is hydrogen; each Y⁵ is hydrogen; each Y⁶is hydrogen; each Y⁷ is hydrogen; each Y⁸ is hydrogen; each Y⁹ ishydrogen; each Y¹⁰ is hydrogen; R² is CH₃; and R³ is CH₃; then R¹ isCH₂D or CHD₂.
 2. The compound of claim 1, wherein each of R¹, R³ and R²is independently selected from CH₃ and CD₃.
 3. The compound of claim 1,wherein each Y¹⁰ is deuterium.
 4. The compound of claim 1, wherein eachY¹⁰ is hydrogen.
 5. The compound of claim 1, wherein each Y⁹ ishydrogen.
 6. The compound of claim 1, wherein each Y⁹ is deuterium. 7.The compound of claim 1, wherein each Y⁸ is hydrogen.
 8. The compound ofclaim 1, wherein each Y⁸ is deuterium.
 9. The compound of claim 1,wherein R¹ is CH₃.
 10. The compound of claim 1, wherein R¹ is CD₃. 11.The compound of claim 1, wherein R² is CH₃.
 12. The compound of claim 1,wherein R² is CD₃.
 13. The compound of claim 1, wherein R³ is CH₃. 14.The compound of claim 1, wherein R³ is CD₃.
 15. The compound of claim 1or 2, wherein each Y¹ is deuterium; each Y² is deuterium; each Y³ isdeuterium; each Y⁴ is deuterium; each Y⁵ is deuterium; each Y⁶ isdeuterium; each Y⁷ is deuterium; each Y⁸ is deuterium; each Y⁹ isdeuterium; and each Y¹⁰ is deuterium.
 16. The compound of claim 1,wherein the compound is selected from the group consisting of thecompounds (Cmpd) set forth in the table below, wherein each Y¹ ishydrogen; each Y² is hydrogen; each Y³ is hydrogen; each Y⁴ is hydrogen;each Y⁵ is hydrogen; each Y⁶ is hydrogen; each Y⁷ is hydrogen; and R³ isCH₃: TABLE Exemplary Embodiments of Formula I Cmpd No. R¹ R² each Y¹⁰each Y⁹ each Y⁸ 101 CH₃ CH₃ H H D 102 CH₃ CH₃ H D H 103 CH₃ CH₃ H D D104 CH₃ CH₃ D H H 105 CH₃ CH₃ D H D 106 CH₃ CH₃ D D H 107 CH₃ CH₃ D D D108 CH₃ CD₃ H H H 109 CH₃ CD₃ H H D 110 CH₃ CD₃ H D H 111 CH₃ CD₃ H D D112 CH₃ CD₃ D H H 113 CH₃ CD₃ D H D 114 CH₃ CD₃ D D H 115 CH₃ CD₃ D D D117 CD₃ CH₃ H H D 118 CD₃ CH₃ H D H 119 CD₃ CH₃ H D D 120 CD₃ CH₃ D H H121 CD₃ CH₃ D H D 122 CD₃ CH₃ D D H 123 CD₃ CH₃ D D D 124 CD₃ CD₃ H H H125 CD₃ CD₃ H H D 126 CD₃ CD₃ H D H 127 CD₃ CD₃ H D D 128 CD₃ CD₃ D H H129 CD₃ CD₃ D H D 130 CD₃ CD₃ D D H 131 CD₃ CD₃ D D D

or a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.17. The compound of claim 1, wherein the compound is selected from thegroup consisting of the compounds (Cmpd) set forth in the table below,wherein each Y¹ is hydrogen; each Y² is hydrogen; each Y³ is hydrogen;each Y⁴ is hydrogen; each Y⁵ is hydrogen; each Y⁶ is hydrogen; each Y⁷is hydrogen; and R³ is CD₃: Cmpd No. R¹ R² each Y¹⁰ each Y⁹ each Y⁸ 200CH₃ CH₃ H H H 201 CH₃ CH₃ H H D 202 CH₃ CH₃ H D H 203 CH₃ CH₃ H D D 204CH₃ CH₃ D H H 205 CH₃ CH₃ D H D 206 CH₃ CH₃ D D H 207 CH₃ CH₃ D D D 208CH₃ CD₃ H H H 209 CH₃ CD₃ H H D 210 CH₃ CD₃ H D H 211 CH₃ CD₃ H D D 212CH₃ CD₃ D H H 213 CH₃ CD₃ D H D 214 CH₃ CD₃ D D H 215 CH₃ CD₃ D D D 216CD₃ CH₃ H H H 217 CD₃ CH₃ H H D 218 CD₃ CH₃ H D H 219 CD₃ CH₃ H D D 220CD₃ CH₃ D H H 221 CD₃ CH₃ D H D 222 CD₃ CH₃ D D H 223 CD₃ CH₃ D D D 224CD₃ CD₃ H H H 225 CD₃ CD₃ H H D 226 CD₃ CD₃ H D H 227 CD₃ CD₃ H D D 228CD₃ CD₃ D H H 229 CD₃ CD₃ D H D 230 CD₃ CD₃ D D H 231 CD₃ CD₃ D D D

or a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.18. The compound of claim 1, wherein the compound is selected from thegroup consisting of the compounds (Cmpd) set forth in the table below,wherein each Y¹ is deuterium; each Y² is deuterium; each Y³ isdeuterium; each Y⁴ is deuterium; each Y⁵ is deuterium; each Y⁶ isdeuterium; each Y⁷ is deuterium; each Y⁸ is deuterium; each Y⁹ isdeuterium; and each Y¹⁰ is deuterium: Cmpd No. R¹ R² R² 300 CH₃ CH₃ CH₃301 CH₃ CH₃ CD₃ 302 CH₃ CD₃ CH₃ 303 CH₃ CD₃ CD₃ 304 CD₃ CH₃ CH₃ 305 CD₃CH₃ CD₃ 306 CD₃ CD₃ CH₃ 307 CD₃ CD₃ CD₃

or a pharmaceutically acceptable salt thereof, wherein any atom notdesignated as deuterium is present at its natural isotopic abundance.19. The compound of claim 1, wherein any atom not designated asdeuterium is present at its natural isotopic abundance.
 20. Apharmaceutical composition comprising the compound of claim 1 or apharmaceutically acceptable salt thereof; and a pharmaceuticallyacceptable carrier.
 21. A method of reducing oxidative toxicity inmitochondria, comprising contacting mitochondria with a compound ofclaim
 1. 22. A method of treating a condition that is Duchenne'smuscular dystrophy or multiple sclerosis, comprising administering to asubject in need of such treatment a compound of claim
 1. 23. The methodof claim 22, wherein the condition is primary progressive multiplesclerosis.
 24. A method of treating a condition that is Duchenne'smuscular dystrophy or multiple sclerosis, comprising administering to asubject in need of such treatment a composition of claim 20.